Methane and nitrous oxide fluxes from four tundra ecotopes in Ny-Ålesund of the High Arctic

During the summers of 2008 and 2009, net methane (CH₄) and nitrous oxide (N₂O) fluxes were investigated from 4 tundra ecotopes: normal lowland tundra (LT), bird sanctuary tundra (BT), the tundra in an abandoned coal mine (CT) and the tundra in scientific bases (ST) in Ny-Ålesund of the High Arctic. Tundra soils in CT (184.5 ± 40.0 μg CH₄/(m²·hr)) and ST (367.6 ± 92.3 μg CH₄/(m²·hr)) showed high CH₄ emissions due to the effects of human activities, whereas high CH₄ uptake or low emission occurred in the soils of LT and BT. The lowland tundra soils (mean, ? 4.4–4.3 μg N₂O/(m²·hr)) were weak N₂O sources and even sinks. Bird activity increased N₂O emissions from BT with the mean flux of 7.9 μg N₂O/(m²·hr). The mean N₂O fluxes from CT (45.4 ± 10.2 μg N₂O/(m²·hr)) and ST (78.8 ± 18.5 μg N₂O/(m²·hr)) were one order of magnitude higher than those from LT and BT, indicating that human activities significantly increased N₂O emissions from tundra soils. Soil total carbon and water regime were important factors affecting CH₄ fluxes from tundra soils. The N₂O fluxes showed a significant positive correlation with ammonia nitrogen (NH₄⁺–N) contents (r = 0.66, p < 0.001) at all the observation sites, indicating that ammonia nitrogen (NH₄⁺–N) content acted as a strong predictor for N₂O emissions from tundra soils. The CH₄ and N₂O fluxes did not correspond to the temperature variations of soil at 0–15 cm depths. Overall our results implied that human activities might have greater effects on soil CH₄ and N₂O emissions than current climate warming in Ny-Ålesund, High Arctic.